2. New signature 91-01 output transformer is an upgrade from the standard 91-01 output transformer. It uses year 2015’s 91-05 model winding method for spacious sound stage and vintage WE iron core material for vintage WE sound.

Within its power limit of 8 watt per channel, 300B single ended amplifier has the least intrinsic distortion among any solid state or tube amplifier designs. 300B single ended amplifier is a dream amplifier for audiophiles and music lovers worldwide. If you can use 8w per channel with your speakers, 300B amplifier is always the no.1 choice.

Sophia Electric’s Richard Wugang redesigned/modified 91-03 stereo amplifier and made the 91-01 in steel chassis for those who wanted for mono-block and at lower budget. The standard version was an instant hit in the market place. Read Jeff Day's Review below:

Positive Feedback Review: "The Sophia Electric Model 91-01 300B mono amps are audiophile dream amps, they have great sonics top to bottom, bass articulation that is the best I've heard, and the SE 91-01 nails all of the nerdy audiophile things like soundstaging, imaging, sense of space, and transparency in such a beguiling way that even music lovers that don't give a rat's ass about audiophile-type sonics will appreciate its prowess.

I recommend these amps heartily, and I'd give them my normal 'two thumbs up' endorsement, but that just wouldn't capture what these Sophia Electric Model 91-01 300B mono amps are capable of, so I've invented a new rating, the 'two hard nipples up' recommendation, which is the highest award I've given out to date." ––– Jeff Day

Sophia Electric has received many custom orders for an upgrade 91-01 mono-blocks with fancier chassis. Richard Wugang redesigned the signature version to fulfill the custom orders. Now this signature version is here for a production model.